Nearly one in seven people in the United States suffer from some type of chronic sleep disorder, and only 50% of people are estimated to get the recommended seven to eight hours of sleep each night. It is further estimated that sleep deprivation and its associated medical and social costs (loss of productivity, industrial accidents, etc.) exceed $150 billion dollars per year. Excessive sleepiness can deteriorate the quality of life and is a major cause of morbidity and mortality due to its role in industrial and transportation accidents. Sleepiness further has undesirable effects on motor vehicle driving, employment, higher earning and job promotion opportunities, education, recreation, and personal life.
Primary sleep disorders affect approximately 50 million Americans of all ages and include narcolepsy, restless legs/periodic leg movement, insomnia, and most commonly, obstructive sleep apnea (OSA). OSA's prevalence in society is comparable with diabetes, asthma, and the lifetime risk of colon cancer. OSA is grossly under diagnosed; an estimated 80-90% of persons afflicted have not received a clinical diagnosis. Secondary sleep disorders include loss of sleep due to pain associated with chronic infections, neurological/psychiatric disorders, or alcohol/substance abuse disorders.
Sleeping disorders are currently diagnosed by two general methods. Subjective methods, such as the Epworth and Stanford Sleepiness Scale, generally involve questionnaires that require patients to answer a series of qualitative questions regarding their sleepiness during the day. With these subjective methods, however, it is found that the patients usually underestimate their level of sleepiness or they deliberately falsify their responses because of their concern regarding punitive action or as an effort to obtain restricted stimulant medication.
The second group of methods uses physiological evaluations, such as all-night polysomnography to evaluate a patient's sleep architecture (e.g., obtaining respiratory disturbance index to diagnose sleep apnea). A polysomnogram (PSG) can also be followed by an all-day test such as the Multiple Sleep Latency Test (MSLT) or its modified version, the Maintenance of Wakefulness Test (MWT). The PSG typically requires patients to spend the night in a sleep laboratory connected to multiple sensors while they attempt to sleep. Because it is conducted in a lab setting, a PSG cannot provide information about a patient's sleeping environment, such as noise, light, or allergens. A PSG also can be difficult to conduct because of a patient's travel concerns or anxiety related to sleeping away from home. Many patients also exhibit a “first night effect” related to a change in sleeping environment. The first night effect often requires a second night in the sleep lab to obtain accurate results. Therefore, the first night effect can easily double the cost of conducting a PSG in a sleep lab.
To combat the difficulties of conducting a PSG in a sleep lab, various methods have been employed to attempt to conduct a PSG test in a patient's home. The systems used in these methods have not been capable of transmitting data. Therefore, these systems have only allowed unattended PSG tests. These methods involve storage of the data to a computer hard disc or other media for the duration of the test. After the test is completed, the media is received, read, and analyzed. Obtaining the data creates an additional delay between completion of the test and the final diagnosis that is not present for a lab-based PSG. Further, unattended tests are plagued with signal failure. In one study involving unattended home PSG, data from over 23% of the patients were unusable due to missing channels, even though a technician called the PSG recording device every 30 minutes to check the quality of the recordings.
None of the current methods for conducting a PSG at home allow transmission of the collected data during the test. All of the current methods require the PSG data to be stored during the test and read only after the test has been completed. As such, the data cannot be periodically or continuously checked for adequacy. Even if the data were periodically evaluated, the current methods do not use a step of allowing a remote monitor to communicate with the subject to correct any sensor/signal problems. The current methods also do not include live video feeds, enabling a remote monitor to visualize the subject during the test. Because of the lack of data availability, communication, and video, the current methods of conducting a PSG at home are by definition unattended sleep studies. It is therefore an object of the present invention to provide a method of conducting a sleep analysis at home wherein the data is transmitted at substantially the same time it that is collected or created. It is another object of the present invention to provide a method of conducting a sleep analysis at home that is remotely attended. It is another object of the present invention to provide a method of conducting a sleep analysis that includes information about the patient's sleeping environment, including environmental factors. It is still another object of the present invention that this method of conducting a sleep analysis be inexpensive.